JPH0586926A - Detector of friction coefficient of running road surface for vehicle - Google Patents

Abstract

PURPOSE:To improve traction control based on a friction coefficient by achieving optimization of the friction coefficient of a running road surface for a vehicle. CONSTITUTION:An optimum friction coefficient is calculated inversely based on the amount of traction control based on an axial torque and on the amount of control based on a slip ratio, while a maximum friction coefficient correction constant is calculated based on the optimum friction coefficient, and by writing the maximum friction coefficient correction constant calculated for updating the former maximum friction coefficient correction constant in a memory means, an optimum maximum friction coefficient correction constant can be read from the memory means, based on an engine driving condition and a maximum friction coefficient. The optimum friction coefficient obtained by the optimum maximum friction coefficient correction factor and the maximum friction coefficient, can be optimized, while the optimum friction coefficient can be detected through a running condition and a road surface condition, and traction control such as the torque control of an engine, and so on, can thus be optimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a friction coefficient of a vehicle running road surface used in traction control of a vehicle, and more particularly to a technique for optimizing the friction coefficient in order to improve the traction controllability.

[0002]

2. Description of the Related Art Conventionally, there has been known a traction control device for improving running stability and acceleration of a vehicle by suppressing an excessive wheel slip that occurs during acceleration of the vehicle. For example, as disclosed in Japanese Patent Laid-Open No. 60-99759, the road surface friction coefficient (road surface μ) at which the wheels contact the ground is estimated, and the engine torque is suppressed according to the road surface μ to improve the acceleration performance. There is something to do. This road surface μ is estimated based on the driven wheel speed.

In such a conventional apparatus, since the road surface μ is estimated based on the driven wheel speed, it is effective in the case of a uniform road surface in which the road surfaces μ of the left and right road surfaces on which the left and right wheels of the vehicle are in contact are equal. However, the road surface μ cannot be accurately estimated on road surfaces having different road surfaces μ on the left and right road surfaces. Therefore, as disclosed in JP-A-1-122763, there is proposed a device for independently estimating the road surface μ on which the driving wheel contacts the ground from the axial torque of the driving wheel.

There is the following device for detecting the road surface μ which estimates the road surface μ from the axial torque. That is, the shaft torque decreases when the drive wheels slip when the engine torque increases or remains constant. Therefore, when a decrease in the shaft torque is detected under the above conditions, it can be detected that the drive wheel has slipped, and the value of the maximum shaft torque immediately before that is the maximum frictional force generated between the drive wheel and the road surface. The maximum frictional force is equal to the value obtained by multiplying the wheel diameter, and the maximum frictional force is obtained from the vehicle specification (weight) and the maximum road surface μ _max. Therefore, if the maximum axial torque is known, the maximum road surface μ _max can be obtained by back calculation. ..

Therefore, during acceleration, the torque sensor attached to the accelerator shaft (or the drive shaft, the propeller shaft, the output shaft of the transmission) monitors the torque loss, and the peak torque value (or the torque acting on the tire at that time). The maximum road surface μ _max is calculated from the value
_The optimum road surface μ (= K · μ _max ) is obtained by multiplying _max by a preset ratio (maximum friction coefficient correction constant K = 0 to 1).
I am trying to ask. Then, traction control such as engine torque control or brake control is executed using this optimum road surface μ.

[0006]

However, in such a conventional road surface μ detecting device, depending on the degree of running condition (slow / rapid acceleration) and road surface condition (high / low μ road),
There is a problem that the optimum road surface μ cannot be detected and the above control cannot be optimized. This will be described with reference to FIG.

When μ = K · μ _max , for example, K =
When set to 0.5, in the high μ road (1), μ ₁ = 0.5 · μ _max1 <μ _min1 (A
Point) On low μ road (2), μ ₂ = 0.5 · μ _max2 > μ _min2 (B
Points). As a result, in the acceleration state like F, high μ
Slip can be well suppressed on the road (1), but not so much on the low μ road (2).

However, in an acceleration state such as E, H,
Since μ ₂ = 0.5 · μ _max2 <μ ₂ '(point C), slip can be suppressed well. Also, at point D, the acceleration performance is poor relative to the road surface condition. In view of the above conventional problems, the present invention aims to optimize the friction coefficient by improving the method of detecting the friction coefficient of the road surface of the vehicle, and improve the traction controllability based on the friction coefficient. With the goal.

[0009]

Therefore, as shown in FIG. 1, an apparatus for detecting a friction coefficient on a road surface of a vehicle according to the present invention includes an axial torque detecting means for detecting an axial torque of a driving wheel of the vehicle. Maximum friction coefficient calculation means for calculating the maximum friction coefficient of the traveling road surface based on the detection signal output from the shaft torque detection means, and the maximum friction coefficient correction constant is assigned according to the operating condition of the engine mounted on the vehicle and the maximum friction coefficient. Storage means for storing, optimum friction coefficient calculation means for calculating an optimum friction coefficient from the maximum friction coefficient calculated by the maximum friction coefficient calculation means and the maximum friction coefficient correction constant, and a slip ratio of the driving wheel Slip ratio calculating means, traction control amount calculating means for calculating a traction control amount based on the shaft torque, and traction control amount based on the slip ratio Traction control amount calculation means for calculating, optimum friction coefficient back calculation means for calculating the optimum friction coefficient from the traction control quantity based on the shaft torque and the traction control quantity based on the slip ratio, and the optimum friction coefficient calculated back by the means. Maximum friction coefficient correction constant calculation means for calculating the maximum friction coefficient correction constant based on the above, and maximum friction calculated by the maximum friction coefficient correction constant calculation means for updating the maximum friction coefficient correction constant stored in the storage means. And a maximum friction coefficient correction constant updating means for writing the coefficient correction constant in the storage means.

[0010]

In this structure, the slip ratio of the drive wheels is calculated, the traction control amount is calculated based on the slip ratio, the axial torque of the drive wheels of the vehicle is detected, and the maximum road surface is detected based on the axial torque. Calculate the friction coefficient. Then, the maximum friction coefficient correction constant is read out, and the optimum friction coefficient is calculated from the maximum friction coefficient correction constant and the maximum friction coefficient. Then, the optimum friction coefficient is calculated back from the traction control amount based on the shaft torque and the traction control amount based on the slip ratio. The maximum friction coefficient correction constant is calculated based on the back-calculated optimum friction coefficient, and the calculated maximum friction coefficient correction constant is written in the storage means to update the maximum friction coefficient correction constant stored in the storage means.

As described above, the optimum maximum friction coefficient correction constant can be read from the storage means by updating the maximum friction coefficient correction constant and writing it in the storage means one after another according to the engine operating condition and the maximum friction coefficient. The optimum friction coefficient obtained by the optimum maximum friction coefficient correction constant and the maximum friction coefficient can be optimized. As a result,
The optimum friction coefficient can be detected by the degree of running condition (slow / rapid acceleration) and road surface condition (high / low friction coefficient road), and it is possible to optimize traction control such as engine torque control or brake control. Become.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. Referring to FIG. 2 showing a system configuration of an embodiment of the present invention, a first throttle valve 4 interlocking with an accelerator pedal 3 is provided in an intake passage 2 of an engine 1 mounted on a vehicle.
And a second throttle valve positioned downstream of the first throttle valve 4 and controlled by an actuator 5 such as an electromagnetic motor.
The throttle valve 6 is interposed.

On the other hand, driving wheel speed sensors 11 and 12 for detecting the rotational speeds of the left and right driving wheels 9 and 10 to which the driving torque from the engine 1 is transmitted via the transmission 7 and the differential gear 8, and the left and right driven wheels 13. Driven wheel speed sensors 15 and 16 for detecting the rotational speeds of the rotary actuators 14, 14, a potentiometer-type throttle sensor 17 for detecting the opening TVO2 of the second throttle valve 6, and a torque sensor 19 as a shaft torque detecting means. A control unit 18 is provided which detects an optimum road surface μ on the basis of a detection signal from each sensor and performs traction control such as engine torque control according to the detected optimum road surface μ.

Next, a method of detecting the road surface μ by the control unit 18 will be described with reference to the flowcharts of FIGS. That is, in FIGS.
In step 1 (abbreviated as S1 in the figure; the same applies hereinafter), the driven wheel speed V _S indicating the vehicle body speed and the drive wheel speed V _D are detected, and in step 2, the driven wheel speed V _S and the drive wheel speed V _S are detected. From V _D , the slip ratio SLIP is calculated by the following equation.

SLIP = V _D −V _S / V _{D In} step 3, the difference ERRS between the target slip ratio SLIPTG and the calculated slip ratio SLIP is calculated. In step 4, the opening value TVO _SLIP of the second throttle valve 6 determined by the difference ERRS is calculated.
In step 5, the torque sensor 19 causes the axial torque T
The RQ is monitored, and in step 6, the maximum road surface μ _max is calculated from the peak value of the shaft torque. In this case, the peak value of the axial torque is equal to the value obtained by multiplying the maximum frictional force generated between the drive wheel and the road surface by the wheel diameter of the drive wheel, and the maximum frictional force is the vehicle specification (weight) and the maximum road surface μ. _The maximum road surface μ _max can be obtained by back calculation if the peak value of the shaft torque is known.

In step 7, the maximum road surface μ
_A preset ratio (maximum friction coefficient correction constant K = 0 to 1) for _{max is} read from a map described later. In step 8, the optimum road surface μ for outputting the engine torque so that the slip ratio is optimally maintained with respect to the maximum axial torque that can be generated is calculated by the following equation. μ = K · μ _{max In} step 9, the engine torque TE is calculated and set for the optimum road surface μ.

In step 10, the shaft torque T
_Opening value TVO _TRQ of the second throttle valve 6 corresponding to RQ
To calculate. In step 11, it calculates the opening value TVO _N of the second throttle valve in the non-slip. In step 12, the TVO _N and the TVO _TRQ are compared, and if TVO _N <TVO _TRQ , the process proceeds to step 13, and if TVO _N ≧ TVO _TRQ , the process proceeds to step 14. In step 13, TVO _N and TVO _SLIP are compared. If TVO _N <TVO _SLIP , the process proceeds to step 15, and if TVO _N ≧ TVO _SLIP , the process proceeds to step 16. In step 14, TVO _TRQ and TVO _SLIP are compared, and if TVO _TRQ <TVO _SLIP , step 17
Proceed to, if TVO _TRQ ≧ TVO _SLIP , step 1
Proceed to 6. In step 15, the opening value TVO2 of the second throttle valve 6, setting the TVO _N. Step 1
6, the opening value TVO2 of the second throttle valve is set to T
Set VO _SLIP . In step 17, TVO _TRQ is set as the opening value TVO2 of the second throttle valve.

In step 18, it is judged whether or not the slip mode is set, and if it is the slip mode, step 1
In step 9, it is determined whether this state is the first time. If it is determined in step 19 that it is the first time, it is determined that the shaft torque has decreased as a result of slippage, and the process proceeds to step 20. Incidentally, if the slip mode is not set in step 19 and if it is not determined to be the first time in step 20, the process returns.

In step 20, the TVO _TRQ and the TV
Calculate the difference ETVO of O _SLIP and proceed to step 21,
Check the engine operating status (acceleration status, etc.). In step 22, the maximum friction coefficient correction constant K is updated. This is executed by the subroutine shown in the flowchart of FIG. That is, in the flowchart of FIG.
In step 30, TVO2 '= TVO _TRQ -ETVO
Is calculated, the process proceeds to step 31, and the engine torque TE ′ determined from the TVO2 ′ is calculated. Step 32
Then, the optimum road surface μ ′ is calculated from the engine torque TE ′, and at step 33, the optimum road surface μ ′ and the maximum road surface μ ′ are calculated.
The K to be updated from the _{ma x} as follows determined by calculating.

K = μ '/ μ _max Returning to the flow charts of FIGS. 3 to 5, in step 23, the K obtained by the above calculation is written in the map for allocating K from the engine operating condition and the maximum road surface μ _max .
Note that in FIG. 9, K in mu _2, K ₂ between written as described above for example mu _1, K ₁ and mu _3, K _{3 2}
Is estimated from the values of K ₁ and K ₃ .

Further, FIG. 7 is a time chart showing the relationship between the shaft torque, the throttle valve opening and the slip ratio at the time of gentle acceleration, and FIG. 8 is the time chart showing the shaft torque, the throttle valve opening and the slip ratio at the time of sudden acceleration. The time chart showing the relationship of is shown. As described above, by updating the maximum friction coefficient correction constant K and writing it in the map one after another, the optimum maximum friction coefficient correction constant K can be read from the map depending on the engine operating state and the maximum road surface μ _max . The optimum road surface μ obtained by the optimum maximum friction coefficient correction constant K and the maximum road surface μ _max can be optimized.

As a result, the optimum road surface μ can be detected depending on the degree of running conditions (slow / rapid acceleration) and road surface conditions (high / low μ road), and traction control such as torque control or brake control of the engine 1 can be performed. It becomes possible to optimize.
3 to 5, step 6 is the maximum friction coefficient calculation means of the present invention, step 8 is the optimum friction coefficient calculation means, step 2 is the slip ratio calculation means, and step 10 is the traction based on the axial torque. The control amount calculation means, step 4 corresponds to the traction control calculation means based on the slip ratio, step 23 corresponds to the maximum friction coefficient correction constant updating means, and step 30 and step 32 in the flowchart of FIG. The step 33 corresponds to the maximum friction coefficient correction constant calculating means.

As described above, the present invention has been described with reference to the specific embodiments, but the present invention is not limited to this, and is attached to the present invention by those skilled in the art. It should be noted that various changes and modifications can be made without departing from the scope of the claims.

[0024]

As described above, according to the present invention,
While calculating the traction control amount based on the slip ratio of the drive wheels, the maximum friction coefficient of the traveling road surface is calculated based on the axial torque of the drive wheels of the vehicle, and the optimum friction coefficient is calculated from the maximum friction coefficient and the maximum friction coefficient correction constant. While calculating the coefficient, the optimum friction coefficient is calculated back from the traction control amount based on the shaft torque and the traction control amount based on the slip ratio,
The maximum friction coefficient correction constant is calculated on the basis of the optimally calculated back friction coefficient, and the calculated maximum friction coefficient correction constant is written in the storage means to update the maximum friction coefficient correction constant stored in the storage means. From this, the optimum maximum friction coefficient correction constant can be read from the storage means according to the engine operating state and the maximum friction coefficient, and the optimum friction coefficient obtained by the optimum maximum friction coefficient correction constant and the maximum friction coefficient can be optimized. Depending on the driving conditions (slow / rapid acceleration) and the road surface condition (high / low friction coefficient road),
The optimum friction coefficient can be detected, and traction control such as engine torque control or brake control can be optimized, which is very useful.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing a routine for detecting an optimum road surface μ according to the present invention.

FIG. 4 is a flowchart showing a routine for detecting an optimum road surface μ according to the present invention.

FIG. 5 is a flowchart showing a routine for detecting an optimum road surface μ according to the present invention.

FIG. 6 is a flowchart showing a subroutine for updating the maximum friction coefficient correction constant K.

FIG. 7 is a time chart showing the relationship among the shaft torque, throttle valve opening, and slip ratio during slow acceleration.

FIG. 8 is a time chart showing the relationship between shaft torque, throttle valve opening, and slip ratio during sudden acceleration.

FIG. 9 is a characteristic diagram showing the relationship between the maximum friction coefficient correction constant K and the maximum road surface μ _max .

FIG. 10 is a characteristic diagram illustrating conventional problems.

[Explanation of symbols]

 1 Engine 1 11 Drive Wheel Speed Sensor 12 Drive Wheel Speed Sensor 15 Driven Wheel Speed Sensor 16 Driven Wheel Speed Sensor 18 Control Unit 19 Torque Sensor

Claims (1)

[Claims] 1. A shaft torque detecting means for detecting a shaft torque of a driving wheel of a vehicle, and a maximum friction coefficient calculating means for calculating a maximum friction coefficient of a traveling road surface based on a detection signal output from the shaft torque detecting means. A storage means for allocating and storing a maximum friction coefficient correction constant according to an operating state of the vehicle-mounted engine and a maximum friction coefficient; a maximum friction coefficient calculated by the maximum friction coefficient calculation means and the maximum friction coefficient correction constant; An optimum friction coefficient calculating means for calculating an optimum friction coefficient from the above, a slip ratio calculating means for calculating a slip ratio of the driving wheels, a traction control amount calculating means for calculating a traction control amount based on the shaft torque, and the slip ratio. Based on the shaft torque, the traction control amount calculating means for calculating the traction control amount, and the traction control amount based on the shaft torque. An optimum friction coefficient back calculation means for calculating the optimum friction coefficient back from the traction control amount based on the ratio, and a maximum friction coefficient correction constant calculation means for calculating a maximum friction coefficient correction constant based on the optimum friction coefficient calculated back by the means, Maximum friction coefficient correction constant updating means for writing the maximum friction coefficient correction constant calculated by the maximum friction coefficient correction constant calculation means to update the maximum friction coefficient correction constant stored in the storage means. A friction coefficient detecting device for a traveling road surface of a vehicle, characterized in that